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What is SIBO and why is it increasingly talked about?
The term SIBO (Small Intestinal Bacterial Overgrowth) refers to an overpopulation of bacteria in the small intestine. Under normal conditions, most microorganisms live in the large intestine, where they perform essential functions. When these bacteria migrate to the small intestine, they can disrupt digestion and cause digestive symptoms: Abdominal discomfort, gas, bloating, or changes in bowel habits are frequent signs, but also very common in other digestive disorders.
What happens in SIBO: an imbalance in the small intestine
In SIBO, bacteria ferment carbohydrates that reach the small intestine prematurely, producing gases that accumulate and generate symptoms. Depending on the type of gas that predominates—hydrogen, methane, or hydrogen sulfide—the different types of SIBO are differentiated, each with a characteristic pattern.
Types of SIBO
- Hydrogen SIBO: is the most frequent. It occurs when bacteria ferment simple sugars, generating hydrogen (H₂). It usually manifests with bloating, abdominal pain, diarrhea, and malabsorption of nutrients. People with hydrogen SIBO often notice a rapid abdominal distension after meals.
- Methane SIBO (also known as IMO): in this case, microorganisms that convert hydrogen into methane (CH₄) predominate. Methane slows down intestinal transit, which is why it is associated with constipation, persistent gas, and a feeling of fullness. It is not considered a “classic” SIBO, since the excess methane often occurs in the large intestine, but its clinical and diagnostic behavior are similar.
- Hydrogen sulfide SIBO: is the least common and also the most complex to identify. The bacteria that cause it produce hydrogen sulfide (H₂S), a gas with a characteristic “rotten egg” odor. It can cause diarrhea, fatigue, brain fog, and strong-smelling stools. In some cases, it coexists with the other types of SIBO.
| Type of SIBO | Predominant Gas | Most Frequent Symptoms | Possible Causes or Associated Profile |
|---|---|---|---|
| Hydrogen | H₂ | Diarrhea, bloating, gas, malabsorption | Altered transit, intestinal dysbiosis |
| Methane (IMO) | CH₄ | Constipation, persistent gas, fullness | Slow transit, chronic constipation |
| Hydrogen sulfide | H₂S | Diarrhea, strong-smelling stools, fatigue | Mixed dysbiosis, protein fermentation |
What about LIBO?
In some cases, the bacterial imbalance is mainly located in the large intestine. This is then called LIBO (Large Intestinal Bacterial Overgrowth) and, although it is not strictly a SIBO, it can produce similar symptoms and be easily confused.
SIBO, IBS, and food intolerances: key differences
SIBO shares symptoms with other frequent digestive disorders, such as irritable bowel syndrome (IBS) or lactose and fructose intolerances. However, their origin is different: while IBS is associated with an alteration of intestinal motility or sensitivity, and intolerances to the digestion of certain sugars, SIBO implies a bacterial imbalance. This similarity of symptoms means that many people take time to identify the real cause of their discomfort. Therefore, accurate diagnosis is essential through specific analyses, which are essential to differentiate and correctly guide the diagnosis.
How it is detected: breath test
The breath test is a non-invasive tool that allows detecting the presence and type of SIBO by measuring the gases produced after ingestion of a specific substrate (such as lactulose or glucose). During the test, the patient blows into several tubes over a certain period and, in each of these samples, the concentration of hydrogen, methane, and hydrogen sulfide is analyzed. The pattern of increase of these gases helps to identify the predominant type of SIBO:
- Elevation of hydrogen → Hydrogen SIBO
- Elevation of methane → Methane SIBO or IMO
- Elevation of hydrogen sulfide → Sulfide SIBO
At Teletest we offer this type of analysis both in a physical center and through at-home kits, with results available in 3–4 days. The results include the measured values and an indicative technical interpretation. In addition, if you need it, we provide you with contact information for specialized healthcare professionals for clinical assessment.
For more information about our tests: 👉 Breath Test
Why an accurate diagnosis makes a difference
Understanding the type of SIBO not only clarifies the cause of the symptoms, but also allows the professional to be guided towards the most appropriate strategy. Laboratory analysis provides an objective and quantifiable basis, especially useful in cases of persistent or confusing digestive symptoms.
SIBO is a complex and increasingly recognized digestive disorder, with different types that can produce similar symptoms but have different mechanisms. Knowing these differences and relying on specific diagnostic tests, such as the Breath Test, is the key to a correct diagnosis.
